Diazotype developing apparatus

ABSTRACT

Apparatus and method for development of two-component diazotype sheets and webs. The developing solution is applied to the moving surface of the exposed diazo paper by the wiping action of a porous applicator pad that is kept damp and replenished by capillary, wicking action through the pad from a developer solution reservoir. The range of application extends from slightly less than 4 grams per square meter to just over 30 grams per square meter. A mechanism may be incorporated in the apparatus for oscillating the applicator surface transverse to the paper travel, such action serving to provide uniform developer application, and thereby eliminating streaking, particularly at low rates of developer application.

United States Patent 1191 Neeb et al. A

1451 Jan. 22, 1974 DIAZOTYPE DEVELOPING APPARATUS [73] Assignee: Diazit Company, Inc., Youngsville,

[22] Filed: Nov. 2, 1971 [211 App]. N0.: 195,074

[52] U.S. Cl. 95/89 R, 118/266 [51] Int. Cl. G03d 5/06 [58] Field of Search 95/89 R, 89 A, 89 G, 94 G,

FOREIGN PATENTS OR APPLICATIONS 1,187,482 2/1965 Germany 95/89 R 988,577 8/1952 France 95/89 R Primary ExaminerFred L. Braun Attorney, Agent, or Firm-Samuelson & Jacob 5 7 ABSTRACT Apparatus and method for development of twocomponent diazotype sheets and webs. The developing solution is applied to the moving surface of the exposed diazo paper by the wiping action of a porous applicator pad that is kept damp and replenished by capillary, wicking action through the pad from a developer solution reservoir. The range of application extends from slightly less than 4 grams per square meter to just over 30 grams per square meter. A mechanism may be incorporated in the apparatus for oscillating the applicator surface transverse to the paper travel, such action serving to provide uniform developer application, and thereby eliminating streaking, particularly at low rates of developer application.

2 Claims, 3 Drawing Figures SHEEI 1 BF 2 PATENTED JAN 2 2 I974 Q v. Mm

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DIAZOTYPE DEVELOPING APPARATUS This invention relates generally to the technology of diazotype reproduction systems, and more specifically relates to apparatus and method for developing twocomponent diazotype materials.

Twocomponent diazotype materials are widely utilized as the light sensitive recording media in numerous diazo reproduction systems. Sheets of such material commonly comprise paper upon which is coated a composition, including a light-sensitive diazonium salt and an appropriate coupling agent, both components being held in a stabilized acidic medium to prevent premature coupling. Following exposure to a light pattern of the intelligence to be reproduced, a latent image is present on the sheets due to decomposition of the diazonium salts in light-struck areas. Development of the imaged materials is now effected by raising the pH of the materials to a point where coupling of the two components can take place, whereby the intense coloration of the resulting azo dyes appears at non-light struck areas, thereby reproducing the original intelligence.

Two basic techniques are utilized to develop the aforesaid two-component materials, viz., the so-called dry method, using the alkaline vapors of ammonia, and the semi-wet" method according to which an alkaline solution is applied directly to the surface of the paper.

In the case of the dry ammonia vapor systems, the basic developing material is very inexpensive and readily available. However, considerable expense and effort are involved in sealing and venting the corresponding equipment to prevent escape of the noxious ammonia vapors. Furthermore, regardless of the success in preventing ammonia vapors from escaping from the apparatus into the surrounding environment, it is still found that an objectionable ammonia smell is present in the finished prints after they leave the machine.

In the semi-wet process, the undeveloped prints are typically coated with an excess of solution which is subsequently squeezed off with rollers, after which the prints are forced dried with hot air. The multitude of precision rollers and the bulk and expense of the drying section which may also require venting tends to make systems of this type impractical for other than large installations.

More recently, apparatus has been proposed for use in semi-wet processes, wherein the developing solution is applied to the imaged paper via a roller surface, which surface in some instances may comprise a rubber blanket to which solution is transferred via intermediate rollers, and which in other instances may comprise porous roller structures the interstices of which are impregnated with the developing solution. In both these types of structures, consistently good results are difficult to achieve in that it is both difficult to transfer uniform quantities of solution from the roller to the imaged surface, and to provide uniform quantities of solution on the rollers to begin with. It is particularly cumbersome with such roller devices, to regulate the rate of developer solution application. Such is typically accomplished by adjusting the nip of the rollers, a process which, in view of roller alignment problems and so forth, tends to be very inexact. Application of a uniform quantity of developer solution by rollers becomes especially inefficient where very low rates of developer flow are employed, and uneven development, streaking and skipping in the resulting prints often ensues. In this latter connection, it should be emphasized, moreover, that low application rates are of the greatest interest in that what is ideally sought to be achieved in semi-wet technology is as dry a process as is possible whereby the developed prints are devoid of limpness, do not curl and so forth, and may be directly stacked and utilized as they emerge from the apparatus.

In accordance with the foregoing, it may be regarded as an object of the present invention, to provide apparatus and method for applying accurately controlled quantities of developer solutions to two-component diazo sheet materials.

It is a further object of the invention, to provide apparatus and method for use in semi-wet development of two-component diazo sheet material, which enables accurately metered application of developer solution over a wide range of flow rates including very low rates thereof, and which accomplishes such result with very simple and inexpensive components.

It is another object of the invention, to provide apparatus and method for semi-wet development of twocomponent diazo sheet material, which enable highly uniform application of developer solution even at very low rates of application, whereby the resulting developed prints are markedly free from streaking and areas of uneven development.

Now in accordance with the present invention, the foregoing objects, and others as will become apparent in the course of the ensuing specification, are achieved in apparatus and method, according to which the developing solution is applied to the moving surface of an exposed diazo paper by the wiping action of a porous application pad that is kept damp and replenished by capillary, wicking action through the pad from a suitable developer solution reservoir in which one end of the pad is immersed. The solution application rate is a function of several readily controlled variables, including the height of the working edge of the applicator over the surface of the developer solution in the reservoir. The range of developer application typically extends from slightly less than 4 grams per square meter to just over 30 grams per square meter. Means may be incorporated in the apparatus enabling oscillation of the application surface transverse to the paper travel, such action serving to provide uniform developer application, and thereby eliminate streaking and skipping, particularly at low rates of developer application.

The invention is diagrammatically illustrated, by way of example, in the drawings appended hereto, in which:

FIG. 1 is a transverse cross-sectional view through a diazotype machine including a developing station in accordance with the present invention;

FIG. 2 is an exploded isometric view of the principal internal components of the developing station and FIG. 3 is a schematic illustration of a feed arrangement for supplying developer solution to the developing station.

In FIG. 1 a diazotype machine appears at l which incorporates developing apparatus in accordance with the present invention. Machine 1, as set forth, actually includes an exposure station, generally designated at 3, which is conventional, and does not, per se, form part of the present invention. Station 3 thus includes an enclosure 5, an exposure drum 7 and a light source 9 therein. A drive shaft 11 carries a roller 13, and an endless belt 17 passes about drum 7 and guides an original 19 and diazo copy sheet 21 introduced into machine 1 in the direction indicated by arrows 23. Following exposure, the original 19 emerges from the machine at path 25 and the imaged diazo copy sheet 21 is passed either manually or by conveyor belt along path 27 to the developing station 29.

As has been previously indicated, the diazo copy sheet 21 herein is of the two-component type, and in accordance with the invention will be developed at station 29 via contact with a liquid developer which will raise the pH in the sensitized coating of the diazo sheet to a point where coupling may occur in non-irradiated areas.

In considering station 29, reference may simultaneously be had to FIG. 2, which is an exploded isometric view of portions of the interior of station 29, and is taken from the left side of FIG. 1. The sheet 21 upon thus entering station 29 at throat 31 is deflected by guide member 33 and thence passes upwardly and contacts slip screen 35. The latter is seen to be anchored at its lower end to enclosure 37 by a bracket 39 and tightening bolt 41, and passes upwardly over a pair of rollers 43 and 45 and the developing solution trough 61 mounted between the rollers. Slip screen is held in contact with rollers 43 and by a pair of resilient pads 47 and 49, of foam rubber or the like, so that the sheet 21 is placed in firm contact with the surfaces of rollers 43 and 45 and is fed in sliding fashion along screen 35 to finally exit from station 29 at discharge port 51 along path 53. As is seen particularly in the exploded view of FIG. 2, as well as in FIG. 1, roller 43 is driven by a chain 54 deriving its power from drive shaft 11 through meshed gears 55 and 56 and sprocket 57. A lateral connecting belt 58 extends between rollers 43 and 45 so that the latter is driven in synchronism with the former. The surface of both rollers 43 and 45 are preferably of metal with an abrasive finish or the like whereby the sheet material undergoing development may be securely grasped during transport.

In accordance with the present invention, development of sheet 21 is effected as the said sheet passes,

. sensitized face downward, across and in contact with the working edge 59 of a porous developer pad 63 mounted in developer trough 61. As may be seen both from FIGS. 1 and 2, developer. trough 61 is a generally rectangular member which extends across the breadth of station 29 in a direction transverse to the movement of the surface to be developed. The trough includes a pair of turned down portions 65 and 67 at its opposite ends which are utilized to secure trough 61 to frame brackets 69 and 71, and thus, in turn, to enclosure 37.

Trough 61 is seen to be of relatively narrow dimension in the direction of paper movement, but to be of considerable vertical extension. The pad 63 effecting development is mounted along one wall 73 of trough 61 and retained at such point by a bracket 75 which rests upon a shelf 79 in opposite wall 81 and is secured to wall 73 by fasteners such as at 77. Pad 63 may be formed of numerous resilient materials, known in the art, including, for example, foamed rubber, plastics, or urethanes or woven and non-woven fabrics or felt-like materials made from both natural and man-made fibers. Other materials will become apparent to those skilled in the art of materials. The principal requirements for the material utilized are that it possess a fine and relatively uniform intersticial structure and possess a relatively smooth surface such that working edge 59 may provide a firm seating contact with the sheet 21 being developed. Pad 63 preferably possesses a generally rectangular shape and is so mounted in trough 61 that its lower edge 83 reposes in developer solution 85 maintained in trough 61, with its upper working edge 59 extending above the upper edge of the trough and contacting slip screen 35. The net result of this arrangement is that sheet material guided along screen 35 is passed with the aid of guide surface 87 over working edge 59 and maintained in contact therewith by slip screen 35.

As has previously been indicated, sheet 21 undergoing development is of the two-component type and accordingly a developing composition is utilized for solution 85 as is appropriate to provide the alkalinity necessary to effect coupling in the sensitized coating of the diazo sheet. The developing composition does not, per se, form part of the present invention but may typically comprise such materials as are known in the art to be useful in semi-wet developing processes, including for example volatile amines such as diethylamine, triethylamine, morpholine or so forth, and particularly nonvolatile organic amines such as ethanolamines, isopropanolamines and various other aliphatic amines.

In accordance with an important aspect of the invention, the rate of application of developing solution to sheet 21 is found to be a controllable function of several readily regulated variables. Most significant in this connection is the fact that liquid transport from the trough 61 is essentially a wicking phenomenon wherein solution 85 is passed upwardly in the wick-like structure represented by pad 63 by capillary action inthe said pad. Such being the case, it will be clear that the rate of liquid movement in the pad is a function not only of the rate of removal at the working edge 59, but of the physical parameters limiting the capillary transport mechanism. Such physical parameters include the intersticial structure of pad 63, the surface tension and viscosity characteristics of solution 85, both of which are controllable, and more importantly the difference in height between the surface 89 of solution 85 and the working edge 59. This last factor is emphasized in that given the relatively deep trough 61 it is clear that the surface 89 may be maintained at highly variable positions, such positions being found to markedly affect the feed rate of solution upwardly in pad 63. In order to provide a desired developer solution feed rate, compatible with a given transport rate for sheet 21, the level of surface 89 may be maintained by any simple feed mechanism, including, for example, the feed arrangement illustrated in FIG. 3 wherein a pump which replenishes the liquid in trough 61 and a drain 121 in the trough placed so as to maintain the desired liquid level 89 by allowing excess developer solution 85 to drain from the trough to an external reservoir 122 to be continuously circulated, or, as another example, by gravity feed from a vertically displaceable reservoir (not shown) mounted internally or externally in relation to station 29.

By varying the several factors cited above, and by further adjusting the rate of transport of sheet material 21 across working edge 59 and by utilizing pads of desired working edge thicknesses, it is found that a very wide range of liquid developer densities may be uniformly applied to sheet material 21. It is thus found that quantities of developer within the range of from slightly less than 4 grams per square meter to just over 30 grams per square meter may be so applied and with relatively uniform covering.

Particularly where developer application rates are utilized which are at the lower end of the above-cited range, it is found that a degree of streaking or skipping may occur during the course of developer application. In accordance with another aspect of the invention, such phenomenom is substantially eliminated by incorporating into the developer apparatus, means for continuously oscillating developer pad 63 transversely to the direction of sheet movement, whereby streaks or skips are, in effect, scrubbed out or erased. Such a technique enables extremely low developer application rates to be utilized, with the retention of readable copy.

In order to achieve the aforesaid oscillations, it is seen from FIG. 2 that downturned portions 65 and 67 include elongated slots 91 which extend transversely to the direction of sheet movement. A pair of pins 93 and 95 pass through such slots and are loosely engaged in holes 97 and 99 in brackets 69 and 71, whereby trough 61 may slide back and forth in the directions of arrow 101 to enable the desired oscillatory movement. The motive force for the oscillations is provided by an electric motor 103 mounted below trough 61. The shaft 105 of motor 103 rotates an arm 107 carrying a pin 109, which thus rotates in a circle. Pin 109 intersects an elongated slot 111 formed in an upturned portion 113 located at the bottom edge of trough 61. Slot 111 extends transversely to slots 91 and it will be clear that as pin 109 is constrained to move in slot 111, the circle executed by such pin will in the course of movement of the pin back and forth in slot 111 drive the trough 61 to and fro along direction 101, to thereby execute the desired oscillatory movements.

While particular embodiments of the invention have been shown and described, it is apparent to those skilled in the art that modifications are possible without departing from the spirit of the invention or the scope of the subjoined claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for developing exposed diazotype sheet material, said apparatus comprising:

a frame;

means for transporting said sheet material at a uniform rate along a prescribed path of travel along the frame;

a reservoir for liquid developer to be applied to the sheet material, said reservoir including a narrow trough mounted upon and extending across the frame;

means for maintaining the level of the liquid in the reservoir at a predetermined constant level;

a porous applicator pad having a first end and a second end, the pad extending into the reservoir so that the first end is located below said predetermined constant level, whereby said first end will be immersed in the liquid developer, and extending above said predetermined constant level so that the second end establishes an extended working edge at a level above said predetermined constant level and intercepting the prescribed path of travel for contacting the sheet material and applying said liquid developer to the sheet material, said working edge being supplied with liquid developer from the reservoir through the pad by capillary action at a rate determined by the difference in levels between the predetermined constant level and the level of the working edge;

said trough having a depth sufficient to provide substantial possible variation in developer feed rate in accordance with the height of the developer surface in the trough with respect to the working surface of the applicator; and

said transport means including a stationary slip screen mounted upon said frame, passing across and contacting the working edge of the pad, and a pair of feed rollers mounted on alternate sides of the working edge in contact with the slip screen, whereby said sheet material may be fed by said rollers along said slip screen and over said working edge.

2. Apparatus in accordance with claim 1, further including means to oscillate said pad transverse to the direction of sheet movement during the transport of said sheet, whereby to oscillate said working edge across said sheet to thereby increase the uniformity of solution application and reduce streaking and skipping in the developed image.

UNITED STATES PATENT OFFICE CERTIFICATE 91% CORRECTION Patent N Dated January 22,

Inventor(s) RObCIt l N001 e1; 1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 55, "station and" should read station;

1 and FIG. 3 should be inserted as shown on the attached sheet.

Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON m. c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 60376-P89 FORM PO-105O (10-69) U.S GOVEFNMENT PRINTING OFFICE: B 69- 9 o UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 a 786 a 736 Dated January 22 1974 Inventor(s) Robert P. Neeb et al. Page 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

FORM PO-10SG [10-69) uscoMM-Dc 60376-P69 U 5 GOVERNMENT PRINTING OFFICE: 9 9 0 i and UNITED STATES PATENT OFFICE Dated January 22, 1974 Patent No. 3 6., 736

Inventor(s) Robert N001) et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 55, "station and" should read station;

FIG. 3 should be inserted as shown on the attached sheet.

Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM P0-1 (10-69) USCOMM-DC 60376-P69 U.S GOVERNMENT PRINTING OFFACE: 8 69- Patent No. ,736 Dated January 22, 1974 Inventor(s) Robert P. Neeb et a1 Page 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

FORM PO-105OHO-9) USCOMM.DC 50375.p5

U 5 GOVERNMENT PRINTING OFFICE I 8 g 9 o 

1. Apparatus for developing exposed diazotype sheet material, said apparatus comprising: a frame; means for transporting said sheet material at a uniform rate along a prescribed path of travel along the frame; a reservoir for liquid developer to be applied to the sheet material, said reservoir including a narrow trough mounted upon and extending across the frame; means for maintaining the level of the liquid in the reservoir at a predetermined constant level; a porous applicator pad having a first end and a second end, the pad extending into the reservoir so that the first end is located below said predetermined constant level, whereby said first end will be immersed in the liquid developer, and extending above said predetermined constant level so that the second end establishes an extended working edge at a level above said predetermined constant level and intercepting the prescribed path of travel for contacting the sheet material and applying said liquid developer to the sheet material, said working edge being supplied with liquid developer from the reservoir through the pad by capillary action at a rate determined by the difference in levels between the predetermined constant level and the level of the working edge; said trough having a depth sufficient to provide substantial possible variation in developer feed rate in accordance with the height of the developer surface in the trough with respect to the working surface of the applicator; and said transport means including a stationary slip screen mounted upon said frame, passing across and contacting the working edge of the pad, and a pair of feed rollers mounted on alternate sides of the working edge in contact with the slip screen, whereby said sheet material may be fed by said rollers along said slip screen and over said working edge.
 2. Apparatus in accordance with claim 1, further including means to oscillate said pad transverse to the direction of sheet movement during the transport of said sheet, whereby to oscillate said working edge across said sheet to thereby increase the uniformity of solution application and reduce streaking and skipping in the developed image. 